This research will examine how hormones and diet influence body maintenance and olfactory communication in a desert rodent - Merriam's kangaroo rat (Dipodomys merriami). I hypothesize that (1) kangaroo rats communicate reproductive state through sand-bathing and urine marking, (2) male hormones control secretion of sebaceous glands that function in body maintenance and as olfactory signals, and (3) green vegetation in the diet of kangaroo rats stimulates release of reproductive hormones which control olfactory communication. When kangaroo rats sand-bathe to remove excess oils from their pelage they leave deposits in the sand that possibly function as olfactory signals. If olfactory deposits at sand-bathing loci communicate reproductive state, males with circulating testosterone should be attracted to sand-bathing sites of receptive females. Castrated and uncastrated males will be tested for their attraction to sand-bathing deposits of estrous and nonestrous females and of castrated and noncastrated males. Sand-bathing deposits probably consist of a mixture of body oils from sebaceous glands associated with the hair and sebum from a specialized sebaceous gland on the animal's dorsal surface. If male hormones control secretions from these glands, the quantity of oil in the hair of reproducing and nonreproducing males may differ; therefore, I will measure and compare quantities of oil in the hair of castrated and noncastrated males. Because reproduction coincides with the growth of green vegetation, release of reproductive hormones may be triggered by diet. Increased urine output that results from consuming green vegetation could also communicate changes in reproductive state. Castrated and noncastrated males will be tested for differences in their preferences for urine of castrated and noncastrated males and females. I will compare animals on a diet of green vegetation and seeds to animals on a diet of seeds alone for differences in gonadal development, quantity of hair oil, and responses to olfactory deposits at sand-bathing loci.